GIS Based Monitoring of Critical Area Upstream Watershed of PB. Soedirman Reservoir, Central Java, Indonesia

Abstract

Upstream watershed has an important role as a conservation area to protect environmental functions for life. The damage of upstream watersheds causes various environmental problems such as soil erosion, landslides, river sedimentation, flooding, and others. Monitoring of upstream watersheds is important to control potential environmental damage. This study used a geographic information system (GIS) for monitoring the critical area upstream of the study site. The aim of this study is to identify critical areas in the watershed by using GIS. Six indicators presented in raster maps such as annual rainfall, soil type, land use type, land slope, population density, and water quality were used to determine the critical area. These indicators were then quantitatively analyzed by using spatial analysis tools of Arc GIS 10.6. Five classes of the critical category were used in this study namely very low, low, moderate, high, and very high. The result showed that 61.74% of the study site was covered by a low class of critical areas. Meanwhile, 37.89% and 0.36% of the study site were covered by moderate and high class critical areas, respectively. Areas with moderate and high class critical areas were found in the eastern part of the study site. The findings of this study provide a reference for determining priority areas for conservation planning.